The decades-old mystery over the fate of Günther Messner - the lost brother of the mountaineering legend Reinhold Messner - was resolved yesterday after DNA tests on a smuggled piece of big toe.

Messner said the tests confirmed that pieces of bone found in a Himalayan glacier had come from his missing brother. Günther disappeared more than 30 years ago while following Reinhold down Nanga Parbat, the world's ninth highest mountain. Ever since their ill-fated 1970 expedition Messner has been haunted by persistent allegations that he abandoned his brother to die as they struggled - frostbitten and delirious - down the mountain's treacherous western slope.

Yesterday Messner said the DNA tests proved his version of events - that Günther, whom he last saw vanish behind a "concave bulge in the snow", had been swallowed up by an avalanche. "My story has finally been vindicated," he said in Austria, flanked by scientists from Innsbruck's Medical Institute who had examined the bone.

His quest to establish the truth about his brother, who was 23, comes after an extraordinary public feud with two members of the expedition, Max von Kiemlin and Hans Saler.

In recent books published in Germany both men claim that after reaching the summit with Günther, Messner sent his brother back down the mountain's perilous Rupal Flank - even though they had nearly died on their way up it. Nobody has managed to climb the same route since.

Messner himself chose to make his way down via the less steep, but uncharted western face. In effect Messner - the first man to climb Everest without oxygen, and often called the world's greatest living mountaineer - had "sacrificed his brother to his own ambition", they wrote.

Over the summer Messner returned to Nanga Parbat. Climbers had previously reported stumbling across the frozen remains of a mountaineer 4,300 metres (14,110ft) up the 8,125-metre peak. Messner trekked to the spot and recognised the shoe and jacket on the body as those of his brother. After burning the remains in a Tibetan ceremony, he took the boot with him - with the bones still inside.

Yesterday Messner admitted he had hidden the bones in four rucksacks before smuggling them out of Pakistan and back to Europe. "For me it was legitimate, even if I didn't follow all the rules," he said.

The location of the body proved that Günther had been descending the mountain's western Diamar face when he was swept away, Messner said, adding: "I had never doubted it. But now we have proof."

Yesterday the professor who carried out the tests told the Guardian that there was a 17.8m-to-one probability the bones had come from Günther Messner.

"We tested a 2.7cm piece of bone, probably from a big toe," Prof Richard Scheithauer, the director of Innsbruck's medical institute, said. He added: "We tested it using the same techniques we recently employed to identify British victims of the tsunami in Sri Lanka."

Messner, a former Italian MEP who represented the German-speaking region of South Tyrol, also achieved fame for his solo ascent of Mount Everest in 1980, and is the first man to climb all 14 of the world's peaks of more than 8,000 metres.

This is not the first time he has come back from the Himalayas with bits of bone. In 2003 he returned from Pakistan with a large leg bone. Tests showed that this bone also belonged to Günther Messner, although it did not establish where he died.